This invention is related to cleaning indoor air and to air handling units used in air conditioning and/or heating systems.
Inside the systems are a fan to move the air, an evaporator or cooling coil or a heating coil, and generally an electric motor with appropriate electrical connections to drive the fan. Inside air handler units for air conditioning purposes there is also a pan and drain line to collect and drain the condensate, and for heating purposes there could be a pan without a drain to hold water to supply moisture to the air.
The inventor developed allergies to inside air, and his doctor supplied shots which provided some temporary relief. However, the allergist advised that the shots would have to be taken for the rest of his life. Lifelong allergy shots were not acceptable. A systematic search for an alternative must be made.
A start was in carefully considering the inside air. In most commercial and residential buildings, inside air problems are partially solved by closing off most of the outside air and correcting the temperature of the inside air.
Molds, mildews and various spores grow very rapidly in the moist, dark, cool environment in the air handlers. Also germs, bacteria, viruses, etc. can be retained or multiply in this unhealthy environment.
In an existing hot water/chilled water system in a house with electronic and electrostatic filters, a count of airborne particles measuring 0.5 microns and higher amounted to 5,000 particles in 1/10th of a cubic foot of air in one minute. That high particle count is unacceptable.
The problem is believed to exist because air handling equipment moves large currents of air around a house or office, office building or residential building, and circulates small particles, notably mold and spores, bacteria and viruses, animal dander and other particles, especially below 100 microns, which are not trapped in the filters.
Typically, an air handling system includes large volume intakes with relatively large dimensions and short intake ducts leading to a plenum and then one or more filters below or before one or more heat exchange coils. A chilling coil is often placed at an angle to the horizontal and is usually in the form of finned parallel tubes connected by short semicircular connectors. Condensation which forms on the outsides of the fins, tubes and connectors runs to edges of the coil where it is collected by a drain pan. Exterior condensate runs down the runs and is collected and carried away by the peripheral drain pan and drain. The condensate, drip pan and drain may be a source of moisture which keeps the dark interior of the air handling system damp. Air is inducted through the intake louvers, intake ducts, plenum and heat exchange coils by a blower, usually a high volume, squirrel cage blower driven by an electric motor. The blower increases the kinetic energy of the heated or chilled air and flows the air out through multiple main and branch ducts to wall, floor or ceiling-mounted registers. Often the intake ducts are larger, shorter and fewer than the main and branch distribution ducts.
To promote effective heat transfer between the air and coils, surfaces around the coils are often lined with heat insulating material. To prevent noise transfer from the air handling equipment to the surroundings, the fan chamber may be lined with sound-absorbing materials.
The dark and often damp interiors of the air handling system provide appropriate conditions for the culture of mold, algae and bacteria, and the profligation of spores, bacteria and viruses.
The problem is exacerbated on the downstream sides of heat exchangers or evaporator coils because the relative humidity is increased by chilling the air. Flowing air entrains moisture condensed on the coils and fins. The excess moisture drops out of the air in downstream parts of the air handlers.
The moisture-mold growth problem is acute in heated air systems in which water is wicked or sprayed, in which a water-bathed drum is rotated, and in which water is cascaded and air is blown through a water curtain. The heated air entrains droplets which fall onto or which are condensed onto cooler surfaces, leaving damp interior surfaces downstream of the fan.
A proposed solution provides an ultraviolet light source between the inlet filter and the heat exchange coil. However, much of the system, and especially the downstream parts beyond the coil, are shaded from the growth-terminating effects of the ultraviolet rays. In some conditions, the plant growth within the air handling system is enhanced by the ultraviolet rays in conjunction with the conditions of available moisture and roughened surfaces and shaded areas of the heat transfer and air handling system.
Needs exist for improved air handling systems which reduce and eliminate fine particles, including mold and spores, and other biological particles from air-circulating systems.